A millimeter wave radar is being utilized for the purposes of automated driving and collision prevention of automobiles.
A millimeter wave radar device is mounted on the front of an automobile, and is equipped with a high frequency module having installed therein an antenna for transmitting and receiving electromagnetic waves, a control circuit for controlling the electromagnetic waves, a housing having the antenna and the control circuit housed therein, and a radome covering the antenna for transmitting and receiving electromagnetic waves (see Background Art of JP-A No. 2007-74662).
The millimeter wave radar device thus constituted transmits and receives millimeter waves with the antenna, so as to detect the relative distance and the relative velocity with respect to the obstacle and the like.
The antenna may receive the electromagnetic waves that are reflected by the road surface and the like other than the target obstacle in some cases, which may provide a possibility of deteriorating the detection accuracy of the device.
For solving this problem, the millimeter wave radar device of JP-A No. 2007-74662 is provided with a shielding member that shields electromagnetic waves between the antenna and the control circuit.
There is described that the shielding member may be an electromagnetic wave absorbing material formed by laminating an electroconductive layer on one of a dielectric loss layer and a magnetic loss layer having a larger dielectric loss than the radome.
There is described that the dielectric loss layer may be formed of at least one carbon material selected from carbon nanotubes, carbon microcoils, shungite carbon, carbon black, expanded graphite, and carbon fibers (see paragraph 0023).
There is described that the magnetic loss layer may be formed of hexagonal ferrite (see paragraph 0023).
There is further described that the dielectric loss layer or the magnetic loss layer preferably contains a substance (an insulating polymer material or an insulating inorganic material) having a higher electric resistivity than the carbon material or the hexagonal ferrite (see paragraph 0024).